In the past, single ended press sealed lamps have been mounted in bayonet type bases using a saurizing cement. The lamp leads were welded to lead extensions, that in turn were soldered or welded to the rim and center contacts of the bayonet base. To focus the lamp, the capsule was moved to its proper location, thereby bending the lead extensions. The region around the press seal, and the remaining volume of the bayonet base were then filled with a saurizing cement. The design has short comings. The attachment of the lead extensions requires several steps in locating the pieces, and in making the welds or solder joints. The lead extensions cost money, take time to install, and are subject to failure. The capsules may be jarred between the time they are focused and the time they are cemented. There may be wire memory, or incomplete bending of the lead extensions, again resulting in inaccurate preservation of the focused location. There is a need for a press sealed lamp, mounted in a base that does not use lead extensions.
Another problem with cement, is that an excess of cement may mound up around the lower end of the lamp capsule. The excess cement may be removed by chipping, or filing it away. The filed region exposed a softer or looser core of material that can subsequently act as a source of cement particles that interfere with lamp contacts, optics, and other equipment. These shed cement particle have caused customers to demand better lamp designs. There is then a need for a press sealed lamp in a base that is not cemented in place.
An alterative prior art form, the lamp capsule was held in a metal retainer. The retainer required the press seal to include locating indentations. The press seal was then fitted into the retainer so the sprung prongs mated with the indentations. The indentations and prongs then positively located and preserved the lamp position. Finally the retainer was crimped, rim to rim to the top edge of the base. The lamp focus was then designed into the structure. There was no opportunity to empirically set the focus. The only way to control the final lamp focus was to accurately manufacture the filament, the support leads, the capsule body, the press seal, the coupler and so forth. If there was any error in the manufacture, there was no opportunity to dynamically relocate the lamp capsule to its proper position. The lead extensions still had to be positioned and welded to the lamp leads, and then welded or solder to their respective base contacts. There is then a need for a focusable lamp.
Examples of the prior art are shown in the following U.S. patents:
U.S. Pat. No. 4,295,076 issued to Fritz Eckart et al on Oct. 13, 1981 shows a metal based bayonet lamp. The press sealed base is pinched in place by a snap in coupler.
U.S. Pat. No. 4,567,397 issued to Deiter Wilhelm et al on January shows a press sealed lamp capsule held in a metal base bayonet lamp. The press seal is braced and clamped in a coupler so as to be fixed in position by the coupler.
U.S. Pat. No. 4,849,670 issued to Paul Hellig et al on Jul. 18, 1989 shows a press sealed lamp capsule held in a metal bayonet type base. The single piece base is notched and indented to form a clamp structure that couples to features of the press seal. The base is also braced against the envelope to thereby positions the lamp capsule.
U.S. Pat. No. 4,869,689 issued to Reinhard Angerer on Sep. 26, 1989 shows abayonet lamp with a press sealed capsule held in a ceramic base.